As a mass flow controller (also referred to as “MFC” hereinafter) for controlling a flow rate of gas used in, for example, a semiconductor process, there has been known a configuration as disclosed in JP-T-2005-531069.
This MFC includes: a flow sensor for measuring a mass flow rate of fluid flowing through a flow passage; a flow control valve for adjusting a mass flow rate of fluid flowing through the flow passage; a control part for controlling the flow control valve based on a flow rate measurement value from the flow sensor and a predetermined set flow rate value; and a communication part for performing communication with an external device. Further, in an internal memory provided in, for example, the control part, there is stored a communication program for controlling the communication part together with a measurement control program for controlling the flow control valve and the like.
Then, the control part is configured so as to receive an updating program transmitted from an external device and update the measurement control program by controlling the communication part based on the communication program.
However, since the measurement control program and the communication program are stored in a single internal memory, in the case where a power source is turned off while updating the measurement control program, not only will the measurement control program crash but also the communication program will crash. Then, there arises a problem that it becomes impossible to perform communication with an external device thereafter.